Pathetic service

I pay Cell C every month and send proof of payment to them but they keep on loosing the payment. Every month I have to phone Cell C as they disconnect the phone ,Now my contract comes to an end and they say I have l monies owing to them so they cannot cancel my contract. I had so many issues with Cell C that I had to close my bank account as well cause of the stupid staff there. Every time they tell me I have got to pay a certain amount I do so for the phone to be connected. Now they tell me have to pay more money. What do the staff at Cell really do. Do they work or just laze around.